1 /*
2 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang;
27
28 import jdk.internal.loader.BuiltinClassLoader;
29 import jdk.internal.misc.VM;
30 import jdk.internal.module.ModuleHashes;
31 import jdk.internal.module.ModuleReferenceImpl;
32
33 import java.lang.module.ModuleDescriptor.Version;
34 import java.lang.module.ModuleReference;
35 import java.lang.module.ResolvedModule;
36 import java.lang.reflect.Layer;
37 import java.lang.reflect.Module;
38 import java.util.HashSet;
39 import java.util.Objects;
40 import java.util.Optional;
41 import java.util.Set;
42
43 /**
44 * An element in a stack trace, as returned by {@link
45 * Throwable#getStackTrace()}. Each element represents a single stack frame.
46 * All stack frames except for the one at the top of the stack represent
47 * a method invocation. The frame at the top of the stack represents the
48 * execution point at which the stack trace was generated. Typically,
49 * this is the point at which the throwable corresponding to the stack trace
50 * was created.
51 *
52 * @since 1.4
53 * @author Josh Bloch
54 */
55 public final class StackTraceElement implements java.io.Serializable {
56
57 // For Throwables and StackWalker, the VM initially sets this field to a
58 // reference to the declaring Class. The Class reference is used to
59 // construct the 'format' bitmap, and then is cleared.
60 //
61 // For STEs constructed using the public constructors, this field is not used.
62 private transient Class<?> declaringClassObject;
63
64 // Normally initialized by VM
65 private String classLoaderName;
66 private String moduleName;
67 private String moduleVersion;
68 private String declaringClass;
69 private String methodName;
70 private String fileName;
71 private int lineNumber;
72 private byte format = 0; // Default to show all
73
74 /**
75 * Creates a stack trace element representing the specified execution
76 * point. The {@link #getModuleName module name} and {@link
77 * #getModuleVersion module version} of the stack trace element will
78 * be {@code null}.
79 *
80 * @param declaringClass the fully qualified name of the class containing
81 * the execution point represented by the stack trace element
82 * @param methodName the name of the method containing the execution point
83 * represented by the stack trace element
84 * @param fileName the name of the file containing the execution point
85 * represented by the stack trace element, or {@code null} if
86 * this information is unavailable
87 * @param lineNumber the line number of the source line containing the
88 * execution point represented by this stack trace element, or
89 * a negative number if this information is unavailable. A value
90 * of -2 indicates that the method containing the execution point
91 * is a native method
92 * @throws NullPointerException if {@code declaringClass} or
93 * {@code methodName} is null
94 * @since 1.5
95 */
96 public StackTraceElement(String declaringClass, String methodName,
97 String fileName, int lineNumber) {
98 this(null, null, null, declaringClass, methodName, fileName, lineNumber);
99 }
100
101 /**
102 * Creates a stack trace element representing the specified execution
103 * point.
104 *
105 * @param classLoaderName the class loader name if the class loader of
106 * the class containing the execution point represented by
107 * the stack trace is named; otherwise {@code null}
108 * @param moduleName the module name if the class containing the
109 * execution point represented by the stack trace is in a named
110 * module; otherwise {@code null}
111 * @param moduleVersion the module version if the class containing the
112 * execution point represented by the stack trace is in a named
113 * module that has a version; otherwise {@code null}
114 * @param declaringClass the fully qualified name of the class containing
115 * the execution point represented by the stack trace element
116 * @param methodName the name of the method containing the execution point
117 * represented by the stack trace element
118 * @param fileName the name of the file containing the execution point
119 * represented by the stack trace element, or {@code null} if
120 * this information is unavailable
121 * @param lineNumber the line number of the source line containing the
122 * execution point represented by this stack trace element, or
123 * a negative number if this information is unavailable. A value
124 * of -2 indicates that the method containing the execution point
125 * is a native method
126 *
127 * @throws NullPointerException if {@code declaringClass} is {@code null}
128 * or {@code methodName} is {@code null}
129 *
130 * @since 9
131 */
132 public StackTraceElement(String classLoaderName,
133 String moduleName, String moduleVersion,
134 String declaringClass, String methodName,
135 String fileName, int lineNumber) {
136 this.classLoaderName = classLoaderName;
137 this.moduleName = moduleName;
138 this.moduleVersion = moduleVersion;
139 this.declaringClass = Objects.requireNonNull(declaringClass, "Declaring class is null");
140 this.methodName = Objects.requireNonNull(methodName, "Method name is null");
141 this.fileName = fileName;
142 this.lineNumber = lineNumber;
143 }
144
145 /*
146 * Private constructor for the factory methods to create StackTraceElement
147 * for Throwable and StackFrameInfo
148 */
149 private StackTraceElement() {}
150
151 /**
152 * Returns the name of the source file containing the execution point
153 * represented by this stack trace element. Generally, this corresponds
154 * to the {@code SourceFile} attribute of the relevant {@code class}
155 * file (as per <i>The Java Virtual Machine Specification</i>, Section
156 * 4.7.7). In some systems, the name may refer to some source code unit
157 * other than a file, such as an entry in source repository.
158 *
159 * @return the name of the file containing the execution point
160 * represented by this stack trace element, or {@code null} if
161 * this information is unavailable.
162 */
163 public String getFileName() {
164 return fileName;
165 }
166
167 /**
168 * Returns the line number of the source line containing the execution
169 * point represented by this stack trace element. Generally, this is
170 * derived from the {@code LineNumberTable} attribute of the relevant
171 * {@code class} file (as per <i>The Java Virtual Machine
172 * Specification</i>, Section 4.7.8).
173 *
174 * @return the line number of the source line containing the execution
175 * point represented by this stack trace element, or a negative
176 * number if this information is unavailable.
177 */
178 public int getLineNumber() {
179 return lineNumber;
180 }
181
182 /**
183 * Returns the module name of the module containing the execution point
184 * represented by this stack trace element.
185 *
186 * @return the module name of the {@code Module} containing the execution
187 * point represented by this stack trace element; {@code null}
188 * if the module name is not available.
189 * @since 9
190 * @see java.lang.reflect.Module#getName()
191 */
192 public String getModuleName() {
193 return moduleName;
194 }
195
196 /**
197 * Returns the module version of the module containing the execution point
198 * represented by this stack trace element.
199 *
200 * @return the module version of the {@code Module} containing the execution
201 * point represented by this stack trace element; {@code null}
202 * if the module version is not available.
203 * @since 9
204 * @see java.lang.module.ModuleDescriptor.Version
205 */
206 public String getModuleVersion() {
207 return moduleVersion;
208 }
209
210 /**
211 * Returns the name of the class loader of the class containing the
212 * execution point represented by this stack trace element.
213 *
214 * @return the name of the class loader of the class containing the execution
215 * point represented by this stack trace element; {@code null}
216 * if the class loader is not named.
217 *
218 * @since 9
219 * @see java.lang.ClassLoader#getName()
220 */
221 public String getClassLoaderName() {
222 return classLoaderName;
223 }
224
225 /**
226 * Returns the fully qualified name of the class containing the
227 * execution point represented by this stack trace element.
228 *
229 * @return the fully qualified name of the {@code Class} containing
230 * the execution point represented by this stack trace element.
231 */
232 public String getClassName() {
233 return declaringClass;
234 }
235
236 /**
237 * Returns the name of the method containing the execution point
238 * represented by this stack trace element. If the execution point is
239 * contained in an instance or class initializer, this method will return
240 * the appropriate <i>special method name</i>, {@code <init>} or
241 * {@code <clinit>}, as per Section 3.9 of <i>The Java Virtual
242 * Machine Specification</i>.
243 *
244 * @return the name of the method containing the execution point
245 * represented by this stack trace element.
246 */
247 public String getMethodName() {
248 return methodName;
249 }
250
251 /**
252 * Returns true if the method containing the execution point
253 * represented by this stack trace element is a native method.
254 *
255 * @return {@code true} if the method containing the execution point
256 * represented by this stack trace element is a native method.
257 */
258 public boolean isNativeMethod() {
259 return lineNumber == -2;
260 }
261
262 /**
263 * Returns a string representation of this stack trace element.
264 *
265 * @apiNote The format of this string depends on the implementation, but the
266 * following examples may be regarded as typical:
267 * <ul>
268 * <li>
269 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java:101)}"
270 * - See the description below.
271 * </li>
272 * <li>
273 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Main.java)}"
274 * - The line number is unavailable.
275 * </li>
276 * <li>
277 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Unknown Source)}"
278 * - Neither the file name nor the line number is available.
279 * </li>
280 * <li>
281 * "{@code com.foo.loader/foo@9.0/com.foo.Main.run(Native Method)}"
282 * - The method containing the execution point is a native method.
283 * </li>
284 * <li>
285 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}"
286 * - The class of the execution point is defined in the unnamed module of
287 * the class loader named {@code com.foo.loader}.
288 * </li>
289 * <li>
290 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}"
291 * - The class of the execution point is defined in {@code acme} module
292 * loaded by by a built-in class loader such as the application class loader.
293 * </li>
294 * <li>
295 * "{@code MyClass.mash(MyClass.java:9)}"
296 * - {@code MyClass} class is on the application class path.
297 * </li>
298 * </ul>
299 *
300 * <p> The first example shows a stack trace element consisting of
301 * three elements, each separated by {@code "/"} followed with
302 * the source file name and the line number of the source line
303 * containing the execution point.
304 *
305 * The first element "{@code com.foo.loader}" is
306 * the name of the class loader. The second element "{@code foo@9.0}"
307 * is the module name and version. The third element is the method
308 * containing the execution point; "{@code com.foo.Main"}" is the
309 * fully-qualified class name and "{@code run}" is the name of the method.
310 * "{@code Main.java}" is the source file name and "{@code 101}" is
311 * the line number.
312 *
313 * <p> If a class is defined in an <em>unnamed module</em>
314 * then the second element is omitted as shown in
315 * "{@code com.foo.loader//com.foo.bar.App.run(App.java:12)}".
316 *
317 * <p> If the class loader is a <a href="ClassLoader.html#builtinLoaders">
318 * built-in class loader</a> or is not named then the first element
319 * and its following {@code "/"} are omitted as shown in
320 * "{@code acme@2.1/org.acme.Lib.test(Lib.java:80)}".
321 * If the first element is omitted and the module is an unnamed module,
322 * the second element and its following {@code "/"} are also omitted
323 * as shown in "{@code MyClass.mash(MyClass.java:9)}".
324 *
325 * <p> The {@code toString} method may return two different values on two
326 * {@code StackTraceElement} instances that are
327 * {@linkplain #equals(Object) equal}, for example one created via the
328 * constructor, and one obtained from {@link java.lang.Throwable} or
329 * {@link java.lang.StackWalker.StackFrame}, where an implementation may
330 * choose to omit some element in the returned string.
331 *
332 * @see Throwable#printStackTrace()
333 */
334 public String toString() {
335 String s = "";
336 if (!dropClassLoaderName() && classLoaderName != null &&
337 !classLoaderName.isEmpty()) {
338 s += classLoaderName + "/";
339 }
340 if (moduleName != null && !moduleName.isEmpty()) {
341 s += moduleName;
342
343 if (!dropModuleVersion() && moduleVersion != null &&
344 !moduleVersion.isEmpty()) {
345 s += "@" + moduleVersion;
346 }
347 }
348 s = s.isEmpty() ? declaringClass : s + "/" + declaringClass;
349
350 return s + "." + methodName + "(" +
351 (isNativeMethod() ? "Native Method)" :
352 (fileName != null && lineNumber >= 0 ?
353 fileName + ":" + lineNumber + ")" :
354 (fileName != null ? ""+fileName+")" : "Unknown Source)")));
355 }
356
357 /**
358 * Returns true if the specified object is another
359 * {@code StackTraceElement} instance representing the same execution
360 * point as this instance. Two stack trace elements {@code a} and
361 * {@code b} are equal if and only if:
362 * <pre>{@code
363 * equals(a.getClassLoaderName(), b.getClassLoaderName()) &&
364 * equals(a.getModuleName(), b.getModuleName()) &&
365 * equals(a.getModuleVersion(), b.getModuleVersion()) &&
366 * equals(a.getClassName(), b.getClassName()) &&
367 * equals(a.getMethodName(), b.getMethodName())
368 * equals(a.getFileName(), b.getFileName()) &&
369 * a.getLineNumber() == b.getLineNumber()
370 *
371 * }</pre>
372 * where {@code equals} has the semantics of {@link
373 * java.util.Objects#equals(Object, Object) Objects.equals}.
374 *
375 * @param obj the object to be compared with this stack trace element.
376 * @return true if the specified object is another
377 * {@code StackTraceElement} instance representing the same
378 * execution point as this instance.
379 */
380 public boolean equals(Object obj) {
381 if (obj==this)
382 return true;
383 if (!(obj instanceof StackTraceElement))
384 return false;
385 StackTraceElement e = (StackTraceElement)obj;
386 return Objects.equals(classLoaderName, e.classLoaderName) &&
387 Objects.equals(moduleName, e.moduleName) &&
388 Objects.equals(moduleVersion, e.moduleVersion) &&
389 e.declaringClass.equals(declaringClass) &&
390 e.lineNumber == lineNumber &&
391 Objects.equals(methodName, e.methodName) &&
392 Objects.equals(fileName, e.fileName);
393 }
394
395 /**
396 * Returns a hash code value for this stack trace element.
397 */
398 public int hashCode() {
399 int result = 31*declaringClass.hashCode() + methodName.hashCode();
400 result = 31*result + Objects.hashCode(classLoaderName);
401 result = 31*result + Objects.hashCode(moduleName);
402 result = 31*result + Objects.hashCode(moduleVersion);
403 result = 31*result + Objects.hashCode(fileName);
404 result = 31*result + lineNumber;
405 return result;
406 }
407
408
409 /**
410 * Called from of() methods to set the 'format' bitmap using the Class
411 * reference stored in declaringClassObject, and then clear the reference.
412 *
413 * <p>
414 * If the module is a non-upgradeable JDK module, then set
415 * JDK_NON_UPGRADEABLE_MODULE to omit its version string.
416 * <p>
417 * If the loader is one of the built-in loaders (`boot`, `platform`, or `app`)
418 * then set BUILTIN_CLASS_LOADER to omit the first element (`<loader>/`).
419 */
420 private synchronized void computeFormat() {
421 try {
422 Class<?> cls = (Class<?>) declaringClassObject;
423 ClassLoader loader = cls.getClassLoader0();
424 Module m = cls.getModule();
425 byte bits = 0;
426
427 // First element - class loader name
428 // Call package-private ClassLoader::name method
429
430 if (loader instanceof BuiltinClassLoader) {
431 bits |= BUILTIN_CLASS_LOADER;
432 }
433
434 // Second element - module name and version
435
436 // Omit if is a JDK non-upgradeable module (recorded in the hashes
437 // in java.base)
438 if (isHashedInJavaBase(m)) {
439 bits |= JDK_NON_UPGRADEABLE_MODULE;
440 }
441 format = bits;
442 } finally {
443 // Class reference no longer needed, clear it
444 declaringClassObject = null;
445 }
446 }
447
448 private static final byte BUILTIN_CLASS_LOADER = 0x1;
449 private static final byte JDK_NON_UPGRADEABLE_MODULE = 0x2;
450
451 private boolean dropClassLoaderName() {
452 return (format & BUILTIN_CLASS_LOADER) == BUILTIN_CLASS_LOADER;
453 }
454
455 private boolean dropModuleVersion() {
456 return (format & JDK_NON_UPGRADEABLE_MODULE) == JDK_NON_UPGRADEABLE_MODULE;
457 }
458
459 /**
460 * Returns true if the module is hashed with java.base.
461 * <p>
462 * This method returns false when running on the exploded image
463 * since JDK modules are not hashed. They have no Version attribute
464 * and so "@<version>" part will be omitted anyway.
465 */
466 private static boolean isHashedInJavaBase(Module m) {
467 // return true if module system is not initialized as the code
468 // must be in java.base
469 if (!VM.isModuleSystemInited())
470 return true;
471
472 return Layer.boot() == m.getLayer() && HashedModules.contains(m);
473 }
474
475 /*
476 * Finds JDK non-upgradeable modules, i.e. the modules that are
477 * included in the hashes in java.base.
478 */
479 private static class HashedModules {
480 static Set<String> HASHED_MODULES = hashedModules();
481
482 static Set<String> hashedModules() {
483
484 Optional<ResolvedModule> resolvedModule = Layer.boot()
485 .configuration()
486 .findModule("java.base");
487 assert resolvedModule.isPresent();
488 ModuleReference mref = resolvedModule.get().reference();
489 assert mref instanceof ModuleReferenceImpl;
490 ModuleHashes hashes = ((ModuleReferenceImpl)mref).recordedHashes();
491 if (hashes != null) {
492 Set<String> names = new HashSet<>(hashes.names());
493 names.add("java.base");
494 return names;
495 }
496
497 return Set.of();
498 }
499
500 static boolean contains(Module m) {
501 return HASHED_MODULES.contains(m.getName());
502 }
503 }
504
505
506 /*
507 * Returns an array of StackTraceElements of the given depth
508 * filled from the backtrace of a given Throwable.
509 */
510 static StackTraceElement[] of(Throwable x, int depth) {
511 StackTraceElement[] stackTrace = new StackTraceElement[depth];
512 for (int i = 0; i < depth; i++) {
513 stackTrace[i] = new StackTraceElement();
514 }
515
516 // VM to fill in StackTraceElement
517 initStackTraceElements(stackTrace, x);
518
519 // ensure the proper StackTraceElement initialization
520 for (StackTraceElement ste : stackTrace) {
521 ste.computeFormat();
522 }
523 return stackTrace;
524 }
525
526 /*
527 * Returns a StackTraceElement from a given StackFrameInfo.
528 */
529 static StackTraceElement of(StackFrameInfo sfi) {
530 StackTraceElement ste = new StackTraceElement();
531 initStackTraceElement(ste, sfi);
532
533 ste.computeFormat();
534 return ste;
535 }
536
537 /*
538 * Sets the given stack trace elements with the backtrace
539 * of the given Throwable.
540 */
541 private static native void initStackTraceElements(StackTraceElement[] elements,
542 Throwable x);
543 /*
544 * Sets the given stack trace element with the given StackFrameInfo
545 */
546 private static native void initStackTraceElement(StackTraceElement element,
547 StackFrameInfo sfi);
548
549 private static final long serialVersionUID = 6992337162326171013L;
550 }